red to furnish
oxygen for the fish. In a well balanced aquarium the water
requires renewal only two or three times a year. It is well to
have an excess of plants and a number of snails, as the snails
will devour all the decaying vegetable matter which would
otherwise poison the water and kill the fish.

[Illustration: Aquarium Finished]

If desired, a centerpiece (A, Fig. 2) can be made of colored
stones held together by cement, and an inverted jar can be
supported in the position shown at B. If the mouth of the jar is
below the surface of the water it will stay filled and allow the
fish to swim up inside as shown. Some washed pebbles or gravel
should be placed on the bottom, and, if desired, a few Chinese
lilies or other plants may be placed on the centerpiece.

** Homemade Pneumatic Lock [65]

Mount an old bicycle hand-pump, A, on the door by means of a metal
plate, B, having a swinging connection at C. Fasten the lever, D,
to the door knob, and make a hinge connection with the pump by
means of a piece of sheet

[Illustration: Pneumatic Door-Opener]

brass, E, soldered to the end of the cylinder. All this apparatus
is on the inside of the door and is connected by a small rubber
tube, F, to a secret mouthpiece placed at some convenient
location. A small piece of spring brass, screwed to the door
frame, will open the door about 1/2 in. when the operator blows in
the mouthpiece, or if the door is within reach of the mouthpiece,
the operator may push the door at the same time that he blows,
thus doing away with the spring, which is only used to keep the
door from relocking.

One way of making the air connection with the outside is to bend
the tube F around and stick it through the keyhole. Few burglars
would ever think to blow in the keyhole.
--Contributed by Orton E. White, Buffalo, N. Y.

** A Homemade Water Motor [66]
By MRS. PAUL S. WINTER

In these days of modern improvements, most houses are equipped
with a washing machine, and the question that arises in the mind
of the householder is how to furnish the power to run it
economically. I referred this question to my husband, with the
result that he built a motor which proved so very satisfactory
that I prevailed upon him to give the readers of Amateur Mechanics
a description of it, hoping it may solve the same question for
them.

A motor of this type will develop about 1/2 hp. with a water
pressure of 70 lb. The power developed is correspondin